Lysosomal storage diseases (LSDs) comprise the most common type of childhood genetic disorder, with an estimated frequency of 1 in 7700 in the general population. It is estimated that 60% of all LSDs have some degree of neurological involvement for which no treatment is available. Thus it is of paramount importance to investigate new approaches to treat neuronopathic LSDs. This work will focus on GM1-gangliosidosis, which is an untreatable childhood disease with moderate to severe neurological impairment caused by a deficiency of lysosomal acid beta-galactosidase (b-gal) with accumulation of GM1-ganglioside in the central nervous system. We will conduct these studies in young adult mice with GM1-gangliosidosis because most LSD cases are diagnosed in early childhood or later when the brain is developmentally equivalent to young adult or adult mice. Experiments in our laboratory and others have shown that AAV8 vectors are exceptionally efficient for gene transfer to the adult mouse brain. Moreover, our studies have shown that AAV8 vectors can transduce the brain microcapillary endothelium after intravascular infusion via the tail vein. Thus AAV8 vectors will be used throughout these experiments. The aims in this application were designed to test the following two hypotheses: 1) De novo expression of mouse b-gal in the thalamus of adult GM1- gangliosidosis mice is sufficient to achieve complete correction of patho-biochemical abnormalities throughout the CMS and normal performance in tests of neuro-motor function; 2) Expression of b-gal in the brain microcapillary endothelium of GM1-gangliosidosis mice will result in wild type levels of GM1- and GA1- ganglioside throughout the CNS and normal performance in tests of neuro-motor function. Here we will inject AAV8 vectors encoding for b-gal or GFP bilaterally into the thalamus of 2 month old GM1- gangliosidosis mice (Aim 1) or deliver AAV8 vectors encoding b-gal or GFP under control of endothelial- or liver-specific promoters via the tail vein (Aim 2). Treated and control mice will be evaluated for neuropathological, biochemical, immunological, and behavioral parameters at different time points over 1 year. We anticipate the findings from these experiments to be applicable to other models of LSDs, and that in the near future they can be evaluated in a large animal model of GM1-gangliosidosis before moving to clinical trials. [unreadable] [unreadable] [unreadable]